Injection pump adjusting structure



Sept. 8, 1964 5. HGFER INJECTION PUMP ADJUSTING STRUCTURE Filed April 2, 1962 FIG] w w w w m I b 2 m ,h I. H w d 7:? All 3 3 I s v a .3 2 a "x 7 n i M 5 a v R W .7 .m# I m N m Z a WM 4 4 In 7% n "I 3,147,746 INJECTION PUMP ADJUSTING STRUCTURE Gerald Htifer, Stuttgart,Germany, assignor to Robert Bosch G.m.b;H., Stuttgart, Germany Filed Apr. 2, 1962, Ser. No. 184,068 Claims priority, application Germany Apr. 1, 1961 4 Claims. (Cl. 123-139) The present invention relates to injection pumps.

More particularly, the present invention relates to a mechanism for adjusting the start of the injection with injection pumps, and is more particularly concerned with injection pumps having a cam drive for producing the fuel delivery operations and of the kind wherein a part located within the pump housing is angularly adjustable relatively to a rotating part in order to adjust the-commencement of the injection'stroke, said mechanism comprising two adjustingpistons of which one' is an outer piston and the other an inner piston which is slidably guided in the outer piston, said pistons being actuated by the delivery pressure of a fuel feed pump as a function of the speed against the resistance of two springs of which one abuts against both of said pistons and tends to displace them in opposite directions, whilst the other abuts against the outer piston and tends to displace it in the direction opposite to that in which it is urged by the delivery pressure of the fuel feed pump. An example of this kind of pump is disclosed by Patent No. 2,902,- 017 (K. A. W. Kemp).

The adjusting mechanism of this known fuel injection pump in which the fuel delivery is controlled by means of a throttle located in the pump inlet passage, is adapted to equalize undesirable alteration of the timing of the fuel injection due to the delivered quantity and to advance the start of the injection with rising engine speed. An object of the present invention is to produce an advance of the timing of the fuel injection, in addition to the advance with rising engine speed, also within the range of the starting speed, that is to say, at a speed which is lower than the lowest running speed. The reason for this is that it has become apparent that many internal combustion engines are easier to start if the injection timing, duringstarting, is advanced relatively to that which obtains with the lowest engine speed.

Although this object has already been realized with a known adjusting mechanism having two coaxially arranged adjusting pistons, this known arrangement, disclosed by Patent No. 2,910,975 (F. M. Evans), requires two additional valves. 7

According to the present invention, in an adjusting mechanism of the kind described above, only the respective working chambers of the two adjusting pistons and which tend to be reduced by the spring abutting against the two adjusting pistons, communicate'through passages with the delivery conduit of the feed pump. Compared with the known arrangement referred to above, the present invention has the advantage that no additional valves are required so thata simpler construction is possible.

The invention will be further described with reference to the accompanying drawings which illustrate one embodiment by way of example in which:

FIG. Us a longitudinal section "of an adjusting mechanism and a cross-section of the corresponding injection FIG. 2 is a graph and shows the adjustment of the start of-the injection as a function of the engine speed.

Referring to the drawings, a cam ring 2 is located in a-housing 1 of a fuel injection pump, and has four cam lobes equi-spaced about its inner contact face. This ring 2 forms one of the parts of acam drive for producing the fuel delivery operations of-the injection pump and is angularly adjustable in order to regulate the start of a fuel United States Patent.

injection stroke. The other part 4 of the cam drive is rotated and serves to guide pushers'5. The contact face of the cam ring 2 cooperates with rollers 6 carried by the pushers. The pushers 5 operate pump pistons 7 which are guided in a cylindrical bore in the part 4', the section of which bore located between the pump pistons 7 forms a pump chamber 8.

An adjuster housing 10 is cast integrally with the pump housing 1 and comprises two adjusting pistons 1 1 and 12' which are coaxially fitted one within the other. The inner piston 11, which is longitudinally displaceable within the outer piston 12, has a cylindrical joint 13 which engages with a lever pin 14 extending from the cam ring 2. The outer piston 12 is longitudinally displaceable inthe housing 10. A spring 15, contained'withinthe outer piston 12, has one end abutting against the base 16 of the piston 12 and its other end against a shoulder 17 of the inner piston'11, thus biasing the two adjusting pistons in opposite directions. In the illustrated position; of the parts, the inner piston 11 abutsunder the action of the spring 15 against a stopper or plug 18 which closes the bore for housing the inner piston 11 in the outer piston 12. 'A second spring 19 has one end abutting against a plug20 which closes the bore for "housing the outer piston 12 in the housing 10, and its other end against a shoulder 22 formed in the outer piston 12. In the illustrated positionof the parts, the spring 19 urges the outer piston 12 towards the base 23 of the housing 10.

\ Extending through the base 23 there is a conduit 24 whichis connected to the delivery conduit of a fuel feed pump, not shown, and which leads into the working chamber 25 of the outer piston 12. A passage 26 in the wall of the piston 12 leads from this working chamber to a longitudinal groove27 formed in the periphery of the inner piston 11, which groove 27 is connected by a radial bore 28 with an 'axial'bore 29 in the piston 11'. The axial bore 29 leads into the working chamber 30 of the inner piston 11. Thus, the working chambers 25 and 30 com municate continuously with'the delivery conduit of the fuel feed pump. The fuel feed pump and the injection pump are both driven by an internal combustion engine, not shown. I j

The end of the outer piston 12, remote from the working chamber 25, extends into a chamber 31 which also: houses the spring 19. This chamber 31 communicates through a groove 32 with a slot 33 formed in the wall of the outer piston 12, through which slot '33 the pin 14 extends. The end of the inner piston 11, -remote fromthe working chamber 30, extends into a chamber 34 which houses the spring15 and which communicatesthrough a groove 35 with the slot 33 in the outer piston 12. This slot 33 comunicates with the inner space 36 of the pump housing 1, which space is filled with fuel and; is connected (by means not shown in'the drawings) through-a fuel return conduit with a fuel supply-tank. I

The operation of the arrangement describedabove is l as follows: V l

The moving parts of the adjusting mechanism are illustrated in the positions-they assume when at rest and during the starting of the internal combustion-engine at a starting speed, which is lower than the idling speed."

The-cam ring 2 is then in a position in which'the fuel injection starts at the angle a (FIG. 2) beforetop dead center (OT) of the internal combustionengine- When the internal combustion engine has started, the pressure p in the fuel deliverypassage of the fuel feed pump and;

therefore, the pressure in the working' chambers 25 and- 30;,- rises to such an extent that, when ;the engine-speed increases from m to n the pressure in thechaniber 30' is capable of overcoming the force of the spring 15 causing the piston 1 1 to move to the left, by the distance a FIG.

1, until it abuts against the base 16 of the outer piston 12.

I 3 During this movement, the cam ring 2 is angularly adjusted in the direction of the arrow 1 (FIG. 1) and the start of the fuel injection is retarded to top dead centre (OT). This setting is retained until the speed n is reached. With a further increase in the engine speed from n to 11 the pressure in the chambers 25 and 30 rises, until it is sufficient to move the piston 12 together with the piston 11 abutting against its base 16, against the force of the biasing spring 19, until the plug 18 has been moved to the right through the distance b and abuts against the plug 20. During this movement, the cam ring 2 is turned against the direction of rotation of the part 4 and the start of the fuel injection is advanced by the angle B.

With decreasing engine speed, the start of the injection is retarded top dead centre when the speed 11 is reached and then again advanced by the angle a. This setting of the start of the injection is also maintained with the engine at standstill and with subsequent starting.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of injection pumps differing from the types described above.

While the invention has been illustrated and described as embodied in automatically adjustable injection pumps, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention, and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In an injection pump, in combination, piston-andcylinder means including a piston member and a cylinder member slidably engaging each other with said piston member located in said cylinder member; cam means operatively connected to said piston-and-cylinder means for axially reciprocating one of said members thereof relative to the other for effecting pressure and suction strokes during which fuel is respectively discharged from and sucked into said cylinder member, said cam means including a camming portion and a follower portion one of which is rotated in a given direction with respect to and rides on the other for effecting said strokes, said other portion of said cam means including a ring; mounting means mounting said ring for free angular movement so as to adjust the angular position of said other portion of said cam means relativeto said one rotated portion thereof in order to regulate the timing of said strokes; an elongated hollow housing connected to said mounting means and having its interior in communication with said ring; an adjusting pin fixed to said ring and extending into said housing so that movement of said pin in said housing will adjust the angular position of said ring;

an outer hollow piston slidable in said housing and an inner piston operatively connected to said, pin and slidable within said outer piston, said housing communicating with a fuel supply pump which is driven by the engine to which fuel is delivered by the injection pump for directing some of the fuel pumped by the fuel supply pump against an'endfaceof said outer piston for urging the latter from one end position in said housing along the interior thereof to an opposite end position; first spring means located in said housing and urging said outer piston from said opposite end position to said one end position in opposition to the fuel pressure so that in its rest position said outer piston is in said one end position thereof; passage means providing communication between the fuel delivered by the fuel supply pump to said housing and an end face of said inner piston for urging the latter in the same direction in which said outer piston is urged by said first spring means, said inner piston when moving in said latter direction acting through said pin on said ring for turning the latter in the same direction that said one portion of said cam means is rotated so as to retard the timing of said strokes, said inner piston being shiftable in said outer piston in said direction of movement toward said one end position of said outer piston until such inner piston reaches a given end position; and second spring means weaker than said first spring means and opposing movement of said inner piston toward said given end position thereof, whereby during the initial starting-up period of the engine said inner piston will move to said given end position thereof while said outer piston remains stationary so that the timing of said strokes will be retarded and when the fuel pressure increases beyond the pressure required to locate said inner piston at said given end position thereof said outer piston will be moved in opposition to said first spring means for advancing the timing of said strokes.

2. An adjusting structure comprising, in combination, an elongated housing communicating at one end with a source of fluid under pressure; an elongated hollow outer piston slidable in said housing and having an end face which defines with said one end of said housing a first chamber for receiving the fluid which is under pressure so that said piston is acted upon at said end face thereof by the fluid, said piston having a closed end distant from said end face thereof; first spring means urging said piston toward said one end of said housing for reducing the volume of said chamber; an inner piston slidable within said outer piston and having one end which defines a second chamber with said closed end of said outer piston, said inner piston being shiftable in said outer piston from one end position where said second chamber is of minimum volume to an opposite end position where said second chamber is of maximum volume, and said inner piston shifting in said outer piston during an increase in the volume of said second chamber in a direction opposite to the direction of movement of said outer piston during an increase in the volume of said first chamber; passage means providing communication only between said first and second chambers so that the fluid under pressure can be located only in said passage means and chambers; second spring means, weaker than said first spring means, urging said inner piston in a direction which reduces the volume of said second chamber and locating said inner piston in a rest position where said second chamber is of minimum volume; and an adjustable element operatively connected to said inner piston to be moved thereby, whereby as the pressure of the fluid increases said inner piston will first move in opposition to said second spring means until the maximum volume of said second chamber is reached, thus moving said element in one direction, and then as the pressure of the fluid continues to increase said outer piston will move in opposition to said first spring means during an increase in the volume of said first chamber, carrying said inner piston with said outer piston while said second chamber remains at its maximum volume, so that the adjustable element is moved first in one direction and then in an opposite direction as the pressure of the fluid continues to increase.

3. The combination of claim 2 and wherein a timing means for adjusting the timing of an injection. pump is operatively connectedto said adjustable element to be adjusted thereby for retarding the timing of the injection pump until the lowest running speed of an engine supplied with fuel by the injection pump is reached and for then advancing the timing when the volume of said first chamber starts to increase, said fluid under pressure being the fluid delivered by a fuel supply pump driven by the engine, so that the timing of theinjection pump will be in an advanced stage until the lowest running speed is reached.

4. In a fuel injection pump, in combination, rotary cylinder means adapted to be rotated about an axis perpendicular to its own axis; piston means slidable in said cylinder means along the axis thereof while rotated therewith; roller means connected to said piston means for rotation therewith; a cam ring having camming portions on which said roller means rides for reciprocating said piston means in said cylinder means during rotation of the latter; mounting means mounting said cam ring for angular adjusting movement so as to adjust the timing of the strokes of the piston means; an adjusting pin fixed to said cam ring and projecting radially therefrom; an elongated housing into which said adjusting pin extends; an inner piston operatively connected to said adjusting pin for moving the latter and said cam ring therewith as said inner piston moves axially; an outer piston in which said inner piston is slidable, said outer piston being coaxial with said inner piston and being axially shiftable in said housing, said outer piston having one end which defines with an end of said housing a first chamber, and said end of said housing communicating with a fuel supply pump driven by the engine to which fuel is delivered by the injection pump and also delivering fuel under pressure to said first chamber, so that the fuel under pressure acts on said one end of said outer piston, said outer piston having an opposite closed end defining a second chamber with one end of said inner piston and said outer and inner pistons being formed with a passage means providing communica- 30 tion between said first and second chambers and limiting the fuel under pressure to a location within said chambers and passage means; first spring means located in said housing and urging said outer piston in a direction which reduces the volume of said first chamber; and second spring means in said outer piston acting on said inner piston and urging the latter in a direction which reduces the volume of said second chamber, and said inner piston when moving with respect to said outer piston in a direction which increases the volume of said second chamber turning said cam ring, through said adjusting pin, in the same direction that said cylinder means is rotated, whereby during an initial starting-up period only the inner piston will move during an initial increase in fuel pressure in opposition to said second spring means to turn said cam ring in the same direction that said cylinder means rotates in order to retard the timing of the strokes of the piston means until the lowest running speed of the engine is reached, while when the fuel pressure increases to become greater than the pressure required to provide said second chamber with its maximum volume the first chamber will increase in volume and said outer piston will shift together with said inner piston, without any relative move ment therebetween, in opposition to said first spring means for turning said cam ring in a direction opposite to the direction of rotation of said cylinder means for advancing the timing of the strokes of the piston means, so that the timing of the strokes of the piston means is advanced during the initial starting-up period.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN AN INJECTION PUMP, IN COMBINATION, PISTON-ANDCYLINDER MEANS INCLUDING A PISTON MEMBER AND A CYLINDER MEMBER SLIDABLY ENGAGING EACH OTHER WITH SAID PISTON OPERATIVELY CONNECTED TO SAID PISTON-AND-CYLINDER MEANS FOR AXIALLY RECIPROCATING ONE OF SAID MEMBERS THEREOF RELATIVE TO THE OTHER FOR EFFECTING PRESSURE AND SUCTION STROKES DURING WHICH FUEL IS RESPECTIVELY DISCHARGED FROM AND SUCKED INTO SAID CYLINDER MEMBER, SAID CAM MEANS INCLUDING A CAMMING PORTION AND A FOLLOWER PORTION ONE OF WHICH IS ROTATED IN A GIVEN DIRECTION WITH RESPECT TO AND RIDES ON THE OTHER FOR EFFECTING SAID STROKES, SAID OTHER PORTION OF SAID CAM MEANS INCLUDING A RING; MOUNTING MEANS MOUNTING SAID RING FOR FREE ANGULAR MOVEMENT SO AS TO ADJUST THE ANGULAR POSITION OF SAID OTHER PORTION OF SAID CAM MEANS RELATIVE TO SAID ONE ROTATED PORTION THEREOF IN ORDER TO REGULATE THE TIMING OF SAID STROKES; AN ELONGATED HOLLOW HOUSING CONNECTED TO SAID MOUNTING MEANS AND HAVING ITS INTERIOR IN COMMUNICATION WITH SAID RING; AN ADJUSTING PIN FIXED TO SAID RING AND EXTENDING INTO SAID HOUSING SO THAT MOVEMENT OF SAID PIN IN SAID HOUSING WILL ADJUST THE ANGULAR POSITION OF SAID RING; AN OUTER HOLLOW PISTON SLIDABLE IN SAID HOUSING AND AN INNER PISTON OPERATIVELY CONNECTED TO SAID PIN AND SLIDABLE WITHIN SAID OUTER PISTON, SAID HOUSING COMMUNICATING WITH A FUEL SUPPLY PUMP WHICH IS DRIVEN BY THE ENGINE TO WHICH FUEL IS DELIVERED BY THE INJECTION PUMP FOR DIRECTING SOME OF THE FUEL PUMPED BY THE FUEL SUPPLY PUMP AGAINST AN END FACE OF SAID OUTER PISTON FOR URGING THE LATTER FROM ONE END POSITION IN SAID HOUSING ALONG THE INTERIOR THEREOF TO AN OPPOSITE END POSITION; FIRST SPRING MEANS LOCATED IN SAID HOUSING AND URGING SAID OUTER PISTON FROM SAID OPPOSITE END POSITION TO SAID ONE END POSITION IN OPPOSITION TO THE FUEL PRESSURE SO THAT IN ITS REST POSITION SAID OUTER PISTON IS IN SAID ONE END POSITION THEREOF; PASSAGE MEANS PROVIDING COMMUNICATION BETWEEN THE FUEL DELIVERED BY THE FUEL SUPPLY PUMP TO SAID HOUSING AND AN END FACE OF SAID INNER PISTON FOR URGING THE LATTER IN THE SAME DIRECTION IN WHICH SAID OUTER PISTON IS URGED BY SAID FIRST SPRING MEANS, SAID INNER PISTON WHEN MOVING IN SAID LATTER DIRECTION ACTING THROUGH SAID PIN ON SAID RING FOR TURNING THE LATTER IN THE SAME DIRECTION THAT SAID ONE PORTION OF SAID CAM MEANS IS ROTATED SO AS TO RETARD THE TIMING OF SAID STROKES, SAID INNER PISTON BEING SHIFTABLE IN SAID OUTER PISTON IN SAID DIRECTION OF MOVEMENT TOWARD SAID ONE END POSITION OF SAID OUTER PISTON UNTIL SUCH INNER PISTON REACHES A GIVEN END POSITION; AND SECOND SPRING MEANS WEAKER THAN SAID FIRST SPRING MEANS AND OPPOSING MOVEMENT OF SAID INNER PISTON TOWARD SAID GIVEN END POSITION THEREOF, WHEREBY DURING THE INITIAL STARTING-UP PERIOD OF THE ENGINE SAID INNER PISTON WILL MOVE TO SAID GIVEN END POSITION THEREOF WHILE SAID OUTER PISTON REMAINS STATIONARY SO THAT THE TIMING OF SAID STROKES WILL BE RETARDED AND WHEN THE FUEL PRESSURE INCREASES BEYOND THE PRESSURE REQUIRED TO LOCATE SAID INNER PISTON AT SAID GIVEN END POSITION THEREOF SAID OUTER PISTON WILL BE MOVED IN OPPOSITION TO SAID FIRST SPRING MEANS FOR ADVANCING THE TIMING OF SAID STROKES. 